Discriminating normal and inflammatory mice models by viscosity changes with a two-photon fluorescent probe

Mechanistic analysis of viscosity-sensitive fluorescent probes for applications in diabetes detection

Diabetes is one of the most detrimental diseases affecting the human life because it can initiate several other afflictions such as liver damage, kidney malfunctioning, and cardiac inflammation. The primary method for diabetes diagnosis involves the analysis of blood samples to quantify the level of glucose, while secondary diagnostic methods involve the qualitative analysis of obesity, fatigue, etc. However, all these symptoms start showing up only when the patient has been suffering from diabetes for a certain period of time. In order to avoid such delay in diagnosis, the development of specific fluorescent probes has attracted considerable attention. Prominent biomarkers for diabetes include abundance of certain analytes in blood serum, e.g., glucose, methylglyoxal, albumin, and reactive oxygen species; high intracellular viscosity; alteration of enzyme functionality, etc. Among these, high viscosity can greatly affect the fluorescence properties of various chromophores owing to the environment sensitivity of fluorescence spectra. In this review article, we have illustrated the application of some prominent fluorophores such as coumarin, BODIPY, xanthene, and rhodamine in the development of viscosity-dependent fluorescent probes. Detailed mechanistic aspects determining the influence of viscosity on the fluorescent properties of the probes have also been elaborated. Fluorescence mechanisms that are directly affected by the high-viscosity heterogeneous microenvironment are based on intramolecular rotations like twisted intramolecular charge transfer (TICT), aggregation-induced emission (AIE), and through-bond energy transfer (TBET). In this regard, this review article will be highly useful for researchers working in the field of diabetes treatment and fluorescent probes. It also provides a platform for the planning of futuristic clinical translation of fluorescent probes for the early-stage diagnosis and therapy of diabetes.

A Single Organic Fluorescent Probe for the Discrimination of Dual Spontaneous ROS in Living Organisms: Theoretical Approach

Single-organic-molecule fluorescent probes with double-lock or even multi-lock response modes have attracted the attention of a wide range of researchers. The number of corresponding reports has rapidly increased in recent years. The effective application of the multi-lock response mode single-molecule fluorescent probe has improved the comprehensive understanding of the related targets' functions or influences in pathologic processes. Building a highly efficient functional single-molecule fluorescent probe would benefit the diagnosis and treatment of corresponding diseases. Here, we conducted a theoretical analysis of the synthesizing and sensing mechanism of this kind of functional single-molecule fluorescent probe, thereby guiding the design and building of new efficient probes. In this work, we discuss in detail the electronic structure, electron excitation, and fluorescent character of a recently developed single-molecule fluorescent probe, which could achieve the discrimination and profiling of spontaneous reactive oxygen species (ROS, •OH, and HClO) simultaneously. The theoretical results provide insights that will help develop new tools for fluorescent diagnosis in biological and medical fields.

Comprehensive monitoring of mitochondrial viscosity variation during different cell death processes by a NIR mitochondria-targeting fluorescence probe

Cell death is a fundamental feature of multicellular organisms, in which mitochondria play crucial roles. Therefore, revealing and monitoring the microenvironment of mitochondria are significant to investigate cell death process. Herein, the mitochondrial viscosity variation behaviors of a series of different cell death processes were monitored with a NIR mitochondria-targeting fluorescence probe FLV. FLV was designed based on a rotatable flavylocyanine fluorophore that presented selective and sensitive NIR fluorescence enhancement response with the increase of environmental viscosity. Fluorescence imaging experiments of living cells incubated with nystatin or under different temperature indicated that FLV was capable of imaging the change of mitochondrial viscosity. Finally, FLV was applied for monitoring the mitochondrial viscosity variation during different cell death processes. It was found that there were obvious mitochondrial viscosity increases during apoptosis, necrosis and autophagy; however, no detectable mitochondrial viscosity variation was observed in ferroptosis process incubated with ferroptosis inducer erastin or RSL3 for 6 h. These results demonstrated that FLV is a viable tool for monitoring the mitochondrial viscosity variation and is likely to be used in the diagnosis of the mitochondrial viscosity-associated cell processes and diseases.

Light, Water, and Melatonin: The Synergistic Regulation of Phase Separation in Dementia

The swift rise in acceptance of molecular principles defining phase separation by a broad array of scientific disciplines is shadowed by increasing discoveries linking phase separation to pathological aggregations associated with numerous neurodegenerative disorders, including Alzheimer’s disease, that contribute to dementia. Phase separation is powered by multivalent macromolecular interactions. Importantly, the release of water molecules from protein hydration shells into bulk creates entropic gains that promote phase separation and the subsequent generation of insoluble cytotoxic aggregates that drive healthy brain cells into diseased states. Higher viscosity in interfacial waters and limited hydration in interiors of biomolecular condensates facilitate phase separation. Light, water, and melatonin constitute an ancient synergy that ensures adequate protein hydration to prevent aberrant phase separation. The 670 nm visible red wavelength found in sunlight and employed in photobiomodulation reduces interfacial and mitochondrial matrix viscosity to enhance ATP production via increasing ATP synthase motor efficiency. Melatonin is a potent antioxidant that lowers viscosity to increase ATP by scavenging excess reactive oxygen species and free radicals. Reduced viscosity by light and melatonin elevates the availability of free water molecules that allow melatonin to adopt favorable conformations that enhance intrinsic features, including binding interactions with adenosine that reinforces the adenosine moiety effect of ATP responsible for preventing water removal that causes hydrophobic collapse and aggregation in phase separation. Precise recalibration of interspecies melatonin dosages that account for differences in metabolic rates and bioavailability will ensure the efficacious reinstatement of the once-powerful ancient synergy between light, water, and melatonin in a modern world.